A slide fastener generally comprises a slide-fastener stringer made up of two slide-fastener halves, each of which has a support tape along and edge of which a coupling element is provided. The coupling element can be continuous, generally helical and formed from a synthetic resin or plastic monofilament, e.g. a nylon or other polyamide or a polyester.
The coupling element is, in turn, formed with a row of interlocking members whose coupling heads project beyond the edge of the tape and are adapted to interdigitate with the coupling element of the other fastener half when a slider is drawn therealong between end stop members. Each coupling head can have a pair of shanks or limbs running inwardly from the edge and the limbs can be chained together by bights or return loops.
A core, e.g. a cord, string or heavy thread of textile material, can extend through the interior of the coupling element and can stabilize the latter, facilitate the attachment to the tape or otherwise provide a structural asset.
A sliding clasp fastener thus can have woven supporting tapes and woven-in prefabricated rows of interlocking members each formed helically from a plastics monofilament, in which the interlocking members, seen in a projection on the plane of the sliding clasp fastener, can have limbs superimposed on at least the interlock side.
Interlocking heads protrude beyond the edges of the supporting tapes, and an inserted core and attachment sections are provided. Each row of interlocking members is attached to the top face of its supporting tape by binding chain threads engaging the interlock side of each interlocking member and at least one wrapping thread engaging the attachment sections and the core and attaching them to the supporting tape.
The binding chain threads are crossed over between successive interlocking members, and the wrapping threads pass round the binding chain threads in a loop between successive interlocking members.
Unlike the so-called woven type of sliding clasp fastener, the rows of interlocking members in the type of sliding clasp fastener with which the invention is connected, are not produced by a weaving process when weaving the supporting tapes, but are in contrast prefabricated and incorporated as completed chains of interlocking members when the supporting tapes are woven. The wrapping threads can be weft threads or chain stitches with a special cross-weave (for example a twill weave).
In the known sliding clasp fasteners of this type which are currently in use, the attachment sections also act as connecting sections between the interlocking members in the row. In other words, they are rearward arcuate links between successive limbs, and seen in the plane of the rows of interlocking members they lie like scales one over the next, and no large U-shaped gaps are left between neighbors.
Consequently, the wrapping threads do not pass through the attachment sections in the middle of the interlocking members, but rather around the rear of the far side from the interlocking heads. The binding chain threads lie away from the interlocking heads, in front of the rearward connecting sections.
This arrangement is not without disadvantages. Where the wrapping threads pass around the connecting sections, they come into contact with the flanks of the operating slider when the sliding clasp fastener is stretched transversely. Thus when the slider is moved the wrapping threads are abraded and undergo premature wear which damages the binding.
Transverse stresses can also displace the array of binding chain threads and wrapping threads which binds the interlocking members, which further aggravates the wear effects on the wrapping threads, caused as described by the slider.
In a different sliding clasp fastener having woven-in prefabricated rows of interlocking members and a core (German Patent document--Open Application No. DE-OS 25 19 829), but having no binding chain threads, wrapping threads encircle the core and the attachment sections, which similarly form parts of the rearward connecting sections.
The same disadvantages arise in this case, even though an additional inlay thread is provided, which lies beneath the row of interlocking members, is laid in grooves in the limbs of the interlocking members, and is bound in together with the interlocking members for the purpose of preventing displacements under transverse stretching.
Finally, the same disadvantages arise in another construction, see German Patent document--Open Application No. DE-OS 28 55 370, in which the rows of interlocking members are not attached to the top of the supporting tapes, but are bound in concentrically and provided with a core. Transverse stretching once again displaces the interlocking members in their binding, with the result that the wrapping threads come into contact with the slider flanks in spite of the inlaid core.